1. Field of the Invention
The present invention relates to a water-proof cover for an inverter unit and in particular to a water-proof cover for a general-purpose inverter unit, in which the cover prevents a splash and jet streams of water from coming into the place around a cooling fan disposed in the wind channel in the unit case of the inverter from the surroundings, while maintaining ventilation performance of the cooling fan.
2. Description of the Related Art
FIGS. 6 and 7 show an example of the structure of a general-purpose inverter unit. Referring to the figures, a unit case 1 comprises a front case 2 and a rear case 3. The front case 2 accommodates a circuit section 4 constructed of electronic parts including a power semiconductor module of the main circuit. The rear case 3 contains a cooling fin assembly 5 of the power semiconductor module that is a heat-generating part, and a cooling fan 6 for ventilating cooling air through the cooling fin assembly 5. The reference symbol 2a designates a piping hole opened in the bottom surface of the front case 2 for wiring cables, and the reference numeral 7 designates an operation panel disposed on the front surface of the front case 2.
The front case 2 accommodating the circuit section 4 is a box type housing covered with side wall surfaces and a ceiling wall surface. On the other hand, the rear case 3 has a wind channel structure combined with the back side of the front case 2, and the top and bottom ends of the rear case 3 opened. A cooling fan 6 is disposed on the top of the rear case 3 and, in operation of the inverter unit, ventilates cooling air through the air channel upward in the unit case 1 and vents the air to the environment as indicated by the arrows in FIG. 7.
The inverter unit may be required to have water-proof in certain environmental condition of the installation location. When an inverter unit is installed together with an outdoor machinery, for example, the inverter unit would be subjected to raindrops or water splash from the machinery side. While the electronic circuit components are contained in the box of the front case 2 enclosed with the walls, the rear case 3 installing the cooling fan 6 has an opening for exhausting cooling air at the top thereof. As a result, a water splash and jet streams of water come onto the cooling fan 6, which is electrical equipment. Consequently, any fault may occur in the electrical components of the cooling fan 6.
In order to deal with this problem, a traditional technology employs a water-proof or, weatherproof container (that is optionally provided) to accommodate the inverter unit therein and places the container in the operation site. Patent Document 1 discloses a specific example of such a container that is a box type casing having metal plates surrounding outer periphery and ceiling surface of the unit case and exhaustion openings of drip-proof performance in the upper side surfaces.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2002-151874 (FIG. 1 in particular)
However, the water-proof container composed of metal plates disclosed in Patent Document 1 requires high material costs and manufacturing costs. Moreover, the container needs large external dimensions in order to ensure a sufficient ventilation path within the container for the cooling air exhausted from the unit case of the inverter unit. As a result, a large space is required for installing the inverter unit in such a container.